(a) Technical Field
The present invention relates to a method for determining an optimal operation point with respect to state of charge (SOC) in a hybrid electric vehicle, which can improve fuel efficiency of the hybrid electric vehicle.
(b) Background Art
Recently, the demand for environment-friendly vehicles has been increased according to the demand for improved fuel efficiency and the stringency of exhaust emission regulations, and thus hybrid vehicles have attracted much attention as a practical alternative.
The hybrid vehicle is defined as a vehicle driven using two power sources, in which a high voltage battery is used as an energy storage device.
The hybrid vehicle includes, as driving power sources, an engine and a motor operatively connected to the engine. It also includes a clutch and a transmission (CVT) for transmitting the driving power, an inverter, a DC/DC converter and a high voltage battery for driving the engine and the motor. In addition, it includes a hybrid control unit (HCU), a motor control unit (MCU) and a battery management system (BMS), which are communicatably connected to each other through a CAN communication.
The high voltage battery is an energy source for driving the motor and the DC/DC converter of the hybrid vehicle, and the BMS for controlling the high voltage battery serves to control the SOC of the high voltage battery by monitoring the voltage, current and temperature of the high voltage battery.
Properly controlling the SOC of the high voltage battery is critically important to safely and effectively operate the high voltage and high capacity battery.
Simply reducing or increasing the use of the motor according to low or high SOC of the battery does not provide an optimal fuel efficiency. There is a need for a new operation strategy that can consider the high or low SOC of the battery and, at the same time, achieve an optimal fuel efficiency level.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.